Apparatus for X-ray analysis having automatic cycling means



JEAN CLAUDE DELARUE July 2:, 195-3 APPARATUS FOR X-RAY ANALYSIS HAVING AUTOMATIC CYCLING MEANS Filed March 25, 1965 '7 Sheets-Sheet l 6 OK W.

y 2, 1963 JEAN-CLAUDE DELARUE 3,393,276

APPARATUS FOR X-RAY ANALYSIS HAVING AUTOMATIC CYCLING MEANS Filed March 25, 1965 '7 Sheets-Sheet Z :mtu

2 5 35 EPQ QQ PMW y 3, 1958 JEAN-CLAUDE DELARUEI 3,391,276

APPARATUS FOR X'RAY ANALYSIS HAVING AUTOMATIC CYCLING MEANS '7 Sheets-Sheet 3 Filed March 25, 1965 5 MHZ lg m W3 2 |\IL... I J E E a Aw 5% i 3 w A M w n G M. M: l .1 r a n A k 1 z 3 n a T. T T. mm m C a 5i! C I T A N w g 2 W V W H J. .3238 5 5 O M 2 3 W 2V Mw V 1 V M A. X M! Q C VA y 2, 9 JEAN-CLAUDE DELARUE 3,391,276

APPARATUS FOR X'RAY ANALYSIS HAVING AUTOMATIC CYCLING MEANS Filed March 25, 1965 '7 Sheets- Sheet 4.

SW mom E N m mmm o8 ON .July 2, 1968 JEAN-CLAUDE DELARUE APPARATUS FGR X-RAY ANALYSIS HAVING AUTOMATIC CYCLING MEANS Filed March 25, 1965 '7 Sheets- Sheet 5 y 1963 JEAN-QLAUDE DELARUE 3,391,275

APPA RATUS'FCR X'RAY .RHAL'X'SIS HAVING AUTOMATIC CYCLING MEANS Filed March 25, 1965 7 Shets-Sheet 6 1968 JEAN-CLAUDE DELARUE 13,391,276

M-YAhATUS FOR X-RAY ANALYSIS HAVING AUTOMATIC CYCLING MEANS Filed March 25, 1965 v Sheets-$heet 7 counf per sec I I Q 8 oo- I \Mm. V1

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3,3illt,2'ili Patented July 2, 1968 3.391.276 APPARATUS FOR X-RAY ANALYSES llAYlNG At-"ltlflL-t'llt IH'HNC Sill-Hi5 .lt'nu-(flnude Delnruc. Arpcuteuil. France. assiguor to (umpnguiu Generale dc Radioiogie, laris, Frnucc, a corporation of l-raucc i ilctl Mar. 25. i965, Ser. No. 442.634 Claims priority, application France, May 26, W64, $68.76 11 Claims. (Cl. 250--5l.5)

ABSTRACT (ll Tllli DESCLOSURE An X-ray generator tube 1 and an imitation detector 2 are disposed in an cvacuable enclosure 4 together with a turntable 3 carrying a number of sample mounts 0 around its eriphery, and indcxable to present each sample in succession at a testing position in which the sample (cl) is irradiated with a primary X-ray beam X from generator 1 and rc-cmits a secondary beam Y into detector 2., which thereupon generates voltage pulses corresponding in amplitude to the atomic numbers of the chemical elements present in the sample. The pulses are passed through an amplitude discriminator which gates pulses of selected amplitude to :2 digital counter which counts the gated pulses over a prescribed time interval as an indication of the concentration of the particular element in the sample. Presettablc automatic control means index the turntable, adjust the X-ray beam voltage, the gating threshold and width, and counting time, and accomplish auxiliary functions in an automatic cycle.

This invention relates to a method and apparatus for the chemical analysis of samples of material by means of X-rays and more particularly to non-dispersive X-ray fluorescence mass spectrometers.

The primary object of the invention has been the provision of practical apparatus whereby the quantitative analysis of samples of matter can be conducted with rapidity yet with high precision under shop conditions, for production inspection and similar purposes. A related object is to provide such apparatus which will operate in a fully automatic manner and yet can be programmed with extreme flexibility, e.g. to permit analyzing dillcrent samples for ditiercnt constituent elements, without impairing the automatic character of the procedure. An object is to provide such apparatus which will be com pact and strong, easily and reliably operated and serviced by unskilled hands, and foolproof in respect to the hazard of irradiation by the X-ray beam used.

l-lighcncrgy radiations (such as X-rays) can be used in various ways for the purpose of quantitative chemical analysis (or mass spectrometry) of a sample of material. The common idea underlying all such methods of analysis with X-rays and the like radiations, is to provoke an interaction between the incident or primary beam, and the atoms of the various constituent elements present in the irradiated sample. The incident photons, if sulliciently energetic, excite the atoms in the sample. The atoms of the constituent elements, when thus excited. emit radiations (so-called X-ray fluorescence) at frequencies which are characteristic of the atoms involved. Hence by analyzing the frequency spectrum of the secondary radiation reemited by the sample as a whole it is possible to analyze the chemical compositions of the sample.

in one class of methods based on this broad principle, the beam of secondary radiation 'rcemitted by the sample is analyzed into its frequency components by selective O ditlraction through a crystal lattie (using the well-known Bragg spectrometer or similar device). The various frequency components in the incident secondary beam are selectively ditlraclcd at various angles, so that by receiving and measuring the amount of radiation diliraetcd in an appropriate direction the proportion of a corresponding COt'lsilltlctll element resent in the sample can be determined. This widely used method has serious drawbacks. Although. the separating or resolving power of such a tlitlraction X-ray spectrometer is high (since it is readily ossible to distinguish between two diilracted rays separated by a very small angular amount), the sensitivity is poor owing to insertion of the dilfracting crystal in the path of the incident (secondary) beam. Also, the inherent geometry of such a spectrometer is such that the solid angle under which the sample is seen from the crystal is very small; in other words the instrument is able to analyze the secondary radiation rcemittcd from only a very small area of the sam le. This further reduces the sensitivity and, moreover, increases the influence of the surface condition of the sample. This last would be a grave deficiency in an instrument designed for high-output work under shop conditions. Moreover, instruments of this class are inherently bulky.

The other important class of X-ray fluorescence mass spectrometers is based on the so-callcd non-dispersive method. Here the entire secondary beam reemitted by the sample is received in a suitable ionization detector of the type usually known as a proportional counter. This is essentially an ionization chamber containing a suitable gaseous atmosphere (cg. argon and methane) such that each frequency component of the incoming secondary beam, corresponding to an element of particular atomic number present in the sample being analyzed, ionizes or excites a number of gas atoms in the counter proportional to the energy content, i.c. frequency value, of said com.- oncnt. The counter thereupon produces a discharge pu s whose voltage amplitude corresponds with the element of said particular atomic number. By subjecting the pulses produced by the proportional counter to an amplitude discriminating step so as to gate only those pulses whose peak amplitude is with a prescribed range corresponding to the atomic numb-er of a selected element present in the sample and counting the gated pulses over a fixed period of time, it is possible to determined the amount of said selected element present in the sample.

This non-dispersive method of Xray analysis has many advantages. It has good sensitivity, permits of utilizing large solid angles and hence large sample areas thereby minimizing the etl'ect of surface defects, and can be embodied in compact, rugged instrumentation. It has however exhibited a serious inferiority as compared to the diffraction methods in respect of resolving power. Elements of closely similar atomic member produce voltage ulscs of closely similar amplitude in the proportional counter, and it has been found diflicult and sometimes impossible to perform the amplittide-discrimination gating operation with sutlicient fineness to permit of an unequivocal separation betwecn such elements positioned close to one another in the periodic table. This dilliculty has been especially great in the case of the lighter elemcnts.

It is among the objects of this invention considerably to reduce this defect of non-dispersive X-ray analysis and improve the resolution achievable therewith, thereby to render this otherwise highly desirable method practically appreciable to the accurate quantitative analysis of chemical elements substantially regardless of atomic number.

Another object is to provide practical workshopdypc apparatus for the automatic quantitative analysis of a large number of samples of material in regard to one or more constituent elements thereof, which will operate on the non-dispersive X-ray fluorescence principle just outlined, and which will be efiicient enough to provide an accuracy amply sufiicient for industrial purposes without requiring the pulses from the proportional counter to be counted over inordinately long periods of time, thus enabling the apparatus to keep step with normal production rates.

- For example, in the application of the apparatus to the determination of sulfur content in samples of tire rubber in a tire manufacturing plant (this being the specific application for which the invention was originally developed), sulfur contents over a range of from 1 to 6% were measured with a relative precision of l0 .using count times of 30 seconds per sample.

Exemplary embodiments of the invention will now be described for purposes of illustration but not of limitation with reference to the accompanying drawings, wherein:

FIG. 1 is a general view, partly in simplified elevation, partly in the form of a functional diagram of an X-ray sample analyzer apparatus according to the invention;

FIG. 2 is a simplified view of the apparatus of FIG. 1 in overhead plan, omitting the units shown in functional form in FIG. 1;

FIG. 3 is a diagram of the automatic control circuitry of the invention;

FIG. 4 is a partial diagram illustrating an improved modification of the automatic control circuitry;

FIG. 5 is a view in selectional elevation showing a practical form of construction of the testing unit of the invention in more detail than FIG. 1;

FIG. 6 is a corresponding view in plan;

FIG. 7 is a selection on line VII-VII of FIG. 6, illustrating the movable X-ray shutter device;

FIG. 8 shows a typical experimental graph of pulsecounts-per-second versus peak amplitudes of the voltage pulses delivered by the proportional counter in response to sulfur content in a sample used for calibration purposes; and

FIG. 9 is an experimental graph in which pulse-countsper-thirty-seconds are pletted versus sulfur content for a number of samples used for calibration purposes.

A general description of the invention will first be given with reference to FIGS. 1 and 2. In FIG. 1, the arrowheaded lines interconnecting various units of the apparatus represent the flow of data and command information between the units. The significance of these interconnections will become fully apparent after the detailed description of the controller unit with reference to FIGS. 3 and 4. Thereafter a practical embodiment of the mechanical section of the apparatus shown in FIGS. 1 and 2 will be described in detail with references to FIGS. 5 to 7. Finally a numerical example of the practical performance of an embodiment of the invention will be given, reference then being made to the graphs of FIGS.- 8 and 9.

Referring to the diagrammatic views of FIGS. 1 and 2, an X-ray analysis apparatus according to the invention comprises an X-ray generator tube 1 and an ionisation counter 2 disposed within a pressure-tight enclosure provided by a domed bell-like cover 4 having its base sealingly engaging a fiat baseplate or table surface 16. A vacuum connection 17 communicating with the enclosure through the surface of table 16 leads by way of a valve 14 to a suitable vacuum pump 10 driven from a motor M1; valve 14 is operable by a solenoid S1 to vent the interior of enclosure 4 to atmosphere.

Also positioned within the enclosure under bell cover 4 is a rotatable sample-carrier turntable 3 carried on the top of a shaft 1'8 sealingly journalled in suitable bearings (not here shown) in the table 16. The shaft 18 at its lower end is coupled to be driven from a suitable electric motor M2 supported underneath the table 16. An indexing wheel 8 carried by shaft 18 underneath the is shown in testing position. FIG. 2 also shows the path.

4 table 16 cooperates with a latch 9 actuated by a solenoid S2 so as to index the shaft 18 and turntable 3 to a number of accurately determined angular positions as will be presently understood. The turntable 3 carries a number of sample mounts uniformly spaced around its periphery. These sample mounts or supports are twelve in number in the illustrative embodiment and may carry respective samples designated 21 to e12. In each of the indexed settings of turntable 3 provided by the indexing arrangement 8-9, a particular one of the samples is located at an analyzing or testing position relative to the X-ray tube 1 and counter 2. In the figures sample e1 of a primary X-ray beam X emitted from the anticathode 19 of the X-ray tube 1 towards the sample in testing position through a window 20 in the X-ray tube casing. A beam of secondary radiation indicated at Y in FIG. 2 is reemitted from the sample such as e1 in testing position in response to the primary X-rays striking it, and enters the ionization counter 2.

It is convenient to have the possibility of opening the cover 4 as for recharging the samples on turntable 3 (as later described in detail) withiut having to cut off the X-ray beam from tube 1. To make this possible without exposing the operator to irradiation, a shutter 5 (omitted from FIG. 1 for clarity) opaque to the X-rays from tube 1 is arranged to be automatically positioned across the X-ray tube exit window 20 whenever the cover 4 is lifted off, and to be removed to a position clear of the window when the cover 4 is replaced. Exemplary mechanism for this purpose is later described.

Before continuing the description, some known theoretical principles of the non-dispersive method of X-ray analysis applied in the invention will be briefly recalled. As in other methods of X-ray analysis, the method is based on a selective interaction of incident X-ray photons with atomic electrons of the respective elements contained in the target sample. The theory of this interaction is very complex, but for the purposes of this discussion the following simplified picture should suffice. On being hit by X-ray photons of suitably high energy from the beam X (FIG. 1) certain electrons in the irradiated sample such as e1 are knocked out of their normal energy states or orbits and the thus excited or ionized atoms a short time later return' to their normal or ground state as the vacant energy states are refilled. In so doing the atoms fiuoresce, i.e. emit rays of a frequency that is a characteristic of the atoms involved. Hence, an analysis of the secondary spectrum reemitted by the target sample 01 can reveal the chemical composition of the sample. In such a spectrum, which is a discontinuous one, the various frequency peaks are indicative of the constituent chemical elements and the amplitudes of the peaks are proportional to the respective concentrations of those elements in the sample.

To efiect this analysis the reemitted or secondary beam Y from the sample e1 is received in the ionization counter tube 2. The counter here used is of the continuous gasfiow, proportional type. Devices of this type are generally conventional and their broad principle of operation is the following.

The counter tube has means (not shown) providing a continuous circulation of a gas mixture (eg argon and 10% methane) therethrough, at a pressure somewhat lower than atmospheric. The tube contains an axial conductor wire 21 connected to a high positive voltage source so as to create a strong radial electric field from the wire to the grounded periphery 22 of the tube. The beam of secondary rays Y reemitted from the sample enters the tube through a window 23 made of a thin sheet of material transparent to the rays. The photons from beam Y excite the atoms of gas in the tube 2 and, through a rather complex process involving Auger transitions and the Townsend avalanche efiect (also known as cumulative or cascade ionization) each incoming photon causes the release of a large number (of the order of e.g. l0") of electrons which are attracted to thc positively charged central conductor 21 and produce a corresponding voltage discharge pulse on the output conductor 24 of the counter tube. The duration of such a discharge pulse may be on the order of 0.1 millisecond.

The :uuplitude of each voltage pulse thus produced on the counter tube output line 24 is rtnvortional to the energy of the incoming photon (from the secondary beam Y) which originated the discharge. llcncc said amplitude is a measure of the frequency of the secondary radiation rccmittcd by the sample r, and therefore (as explained above) an indication of the particular chemical constituent clement responsible for the discharge. The rate at which the pulses occur per second is proportional to the amount of the particular constituent in the sample.

Therefore, by counting over a given period of time (say 30 seconds) the number of pulses of various amplitudes present on the ionization detector output line 21., the chem icalcomposition f the sample can be ascertained.

It will he understood that the counter 2 will normally deliver, over a given period of time, irregularly spaced, interspersed series of pulses of the. various amplitudes corresponding to the chemical constituents of the sample, witlt the total number of pulses of each amplitude statistically corresponding to the relative proportions of the constituent elements. Usually, however. it is desired to test for a single constituent element at a time. and for this purpose it is necessary to count only those voltage pulses whose amplitudes lie between certain prescribed upper and lower limits so selected as to include only those pulses corresponding to the desired element. The count obtained will then represent a measure of the amount of that element present in the sample.

To illustrate the above by means of an example, reference is made to FIG. 8 which shows part of a graph in which the abscissa are voltages and the ordinates are pulse counts per second. The graph represents a Gaussian distribution curve of pulse counts corresponding to the atoms of sulfur present in a test sample of graphite used for calibration purposes. It is seen that the voltage s read at rnid-altitudc of the curve is from Vl::46 volts to V2:64 volts.

This means that if the voltage pulses occurring on the counter output line. 24 are amplitude-diseriminated and gated so as to pass only those voltage peaks greater than- V1 and less V2 and only the gated pulses are counted, the count per second (or other given time interval) will be proportional to sulfur content in any sample used as a target.

To perform this selective. amp]itudc-discriminative gating function, the line 24 is applied to an amplitude-discriminating unit schematically shown at 11. Unit 11 cssentially comprises a preamplifier in which the pulses applied over line 24 are preamplified, and voltage gating means in which the prcamplified pulses are compared to selectable upper and lower reference voltage levels V2 and V1. The unit It is schematically shown provided with the two controls 25 and 26, such as potentiometer knobs, which serve respectively to preset the lower or gating threshold voltage (above termed VI), and the gate width (AV-:V2V1). Adjustment of the controls 25 and 26 can therefore serve to preset the lower and upper limits of the voltage peaks that are allowed to pass from the counter tube output line 24 to the output of the amplitudediscriminatorcircuit 11. It will be understood from earlier explanations that this dual adjustment makes it possible to pass to the outputof circuit 11 only those discharge pulses from the ionization detector or counter tube 2 that represent responses of said counter tube produced by the atoms of a particular element (say sulfur) that it is desired to titrate in the sample exposed to the X-ray beam X from X-ray tube 1.

The pulses thus selectively gated are passed from circuit 11 to a digital counter circuit 12, such as a conventional decade counter. Counter circuit 12 is shown provided with a control 27 which is adjustable to preset the time interval over which a count is made. With control 27 adjusted to a given time interval (say thirty seconds), it will be evident that the count indication given by counter circuit 12 for each of the samples c -e positioned at the testing station (as shown for sample 0 in FIG. 2) will be a funci f h amount f the element (say sulfur) selected by means of the amplittide-discriminator controls 25-26, in the particular sample. The count indications given by counter circuit 12 may he recorded in any lesircd manner, and as here shown said indications are applied to a print.- ing unit schematically shown at 13.

In a non-dispersive X-ray fluorescence method of analysis, of the class to which the process of the invention broadly pertains, a serious problem has existed in connection with the separating or resolving power achievable. The characteristic spectral lines of the secondary X-ray beam (indicated as Y in FIG. I) reemitted by the atoms of any element present in the specimen and received in ionization counter tube 2, have frequencies that are proportional to the atomic number of the element (h'loselcys law). Hence, should the specimen contain constituent elements whose atomic numbers differ by relatively small amounts, the discharge pulses produced on line 2-8 by the responses of the atoms of such neighboring elements to the primary X-ray beam X will not differ tnuch in their voltage peak values, and there may be ditliculty in discriminating between such pulses by adjustment of the threshold and gatcavidth voltages in the amplitude discriminator circuit 11 (through adjustment of controls 25, 7.6). This difficulty would be especially serious in connection with elements of relatively low atomic number, that is to say the lighter elements.

In accordance with a feature of the invention, the resolving power of the apparatus is substantially increased and its usefulness for the quantitative analysis of light elements enhanced, by providing as the source of primary X-ray beams an X-ray tube 1 having means for accurately regulating its high-tension supply voltage, and adjusting said voltage to a level high enough so that the resulting primary beam from Xa'ay tube 1 will be capable oi exciting the atoms of the selected element but not so high that said beam will excite any elements of substantially higher atomic number. By this expedient the ionization counter 2 can be prevented from delivering on line 24 any discharge pulses due to the responses of atoms of any heavier elements that may be present in the tested specimen. The task of the amplittide-discriminator 11 is thereby facilitatcd and its functioning made more cf'lect'ive in that its voltage controls 25, 26 need simply be adjusted to discriminate against those elements present in the sample that are lighter than the selected element.

For this purpose, the voltage supply unit for X-ray tube. 1, which is schematically shown at 15, comprises a suitable high voltage power generator together with means for precisely regulating voltage (and current) values of the generated power and means for prcselccting said voltage and current values. Controls for presclccting the voltage and current of the hightcnsion supply 15 are schematically shown at 28 and 29 respectively.

Means are provided in accordance with the invention for automatically controlling the operation of the system so far described in accordance with a prescribed sequence and including flexible means for modifying such sequence. The automatic control or programming means is schematically represented in FIG. 1 as the unit 6, and will now be described in detail with reference to the diagram of FIG. 3.

In this diagram, components designated by the same rcfrences as components shown in FIGS. 1 and 2, are to be identified with these latter even though they may be represented by somewhat different symbols. For the sake of botlt brevity and clarity, the circuitry of FIG. 3 will first be described in its broad lines only, and the disclosure will tltereaftcr be pursued with reference to the operation of the system, the various circuit components being referred to as they participate in this operation.

Connected across the alternating network ltlll-is the primary winding of a supply transformer 101 having two \g'grmrlgttics; 1(12, 1113, Also connected across the network 100 it; a motor l\l3.which serves to drive a fun, not shown, acting to circulate the mixture of argon and methane previously referred to through the cmninuousdlow, propottiontti ionization detector or counter 2. A general cutort switch 104 is connected between one terminal of networl; ltlt) and the junction of motor M3 and the primary oi transformer 18!.

'lranstormcr secondary 102 delivers 220 volts in the example across the A-C supply lines 105, 106. This 220 still alternating power across 195-166 serves to cnct'gin inter alia the 10ilOWll1g components connected in parallel across said lines:

Vacuum pump motor M1 which drives the vacuum pump 10 (FIG. 1) for evacuating the enclosure under bell cover 4;

Solenoid S1 serving (when dcencrgizcd) to operate the valve 14 to cut oil the vacutun connection and vent the enclosure 4 to atmosphere instead.

Turntable motor M2 which through indexing gear 8 rotates the sample'carrier turntable 3.

Also connected across the 2'10 volt A-C lines 105-106 is a fullwave rectifier bridge circuit 167 which has its DC output terminals connected across the latch-operating solenoid S2, of latching device 9 (FIG. 1).

The AC lines 105, 106 are also connected in parallel to energize the inputs of a pair of monostable circuits No. 1 and No, 2, the functions of which will appear later.

The supply transformer secondary 103 delivers 24 volts energy which is applied to a full-wave rectifier bridge 110 having its positive output terminal grounded and its negative output terminal connected to a D-C supply line 111.. This D-C supply line serves to energize a number of relay windings and other components which serve to con trol the automatic operation of the system in a manner that will stand out from the en i g e crip ion of a est rocedure.

It is assumed that the various units 11, 12, 13, 15 of the system shown in FIG. 1 are under power and that samples have been inserted on the turntable 3. The amplitude discriminator controls 25, 26 are adjusted in accordance with the element to be tested [or in the samples as earlier explained it being first assumed that all twelve specimens r samples e1-e12 are to be tested for the proportions of a common element therein, say the proportion of sulfur in specimens of tire rubber. The voltage control 28 of the power supply unit 15 is also adjusted as to cut off all voltage peaks from ionization detector tube 2 corresponding to constituent elements of higher atomic numbers, and the current control 29 is adjusted to a suitable value such that the ionization detector 2 will reach saturation for a concentration of the tested element in the samples somewhat greater than the highest concentration values to be expected, The cover :1 is tien lowered to scaling position, this action automatically moving the shutter clear of the path of X-ray beam X from the X-ray tube 1 (as later described in detail).

After these preliminary operations have been performed, general switch 104 is closed, This energizes fan motor M3 to blow a stream or gas comprising 90% argon and methane through the ionization detector tube 2. Power is simultaneously applied across each of the secondary windings 102 and 103. The voltage present across secondary 103 is rectified by bridge 1.1.0 and applies negative voltage (24 v.) to the D-C supply line 111. This has the following cilccts.

A relay winding R9 is energized through a circuit leading from DC line 111 through winding R) and thence to ground by way of two paths in parallel: the one through a revcrser switch r7a in normal position, the other through a rcverscr switch .vwl now in the position shown for reasons that will later appear. Energization of relay winding R9 opens the normallyclosed relay contacts r90, thereby preventing cncrgization of a stepping solenoid S3, and simultaneously closes the Oi nially-opcn contacts 191), preparing a path from step ping-switch arm 112 to ground. Stepping switch arm 112 cooperates with twelve switch segments Nos. 1 to 12 corresponding to the twelve indexing positions of the turntable 3.

A start-cycle switch K1 is now manually closed, onergizing relay winding R1. This winding remains energized on release of the start-cycle switch through a holding circuit including normally-closed relay contacts rda and relay contacts r111, now closed due to cuergization of R1.

Encrgization of relay R1v closes contacts rib thereby energizing vacuum valve solenoid S1 and vacuum pump motor Ml, whereby vacuum valve 14 is shiited to disconnect the enclosure from atmosphere and connect it to the output of vacuum pump it), and said pump is operated to evacuate the enclosure.

A delayed-action relay T is energized 0n energization of R1 by way of the contacts r3a and r351, both in their normally closed positions, and contacts ria now closed. After a determined delay period, 105 seconds in this example, contacts 1 associated with the delayed-action relay T are closed, whereupon a relay R3 is energized by way of said contacts I, normally closed contac s rlia and contacts r111 now closed.

On energization of R3, holding contacts r31) are closed to provide a holding circuit for R3 through r31) and normallycloscd contacts r812. Energization of R3 also closes normally open contacts r3c, thereby connecting ground by way of previously closed contacts r9!) to the rotary switch arm 1.12.

Switch arm 112 is at this time engaging step contact N0. 1, so that the ground potential is applied through said step contact and a diode 1.18 to a lamp L, shorting out a resistance 117 and permitting full illumination of the lamp. The ground potential on sw el a U?- s also applied through step contact No. 1 and a diode 119 to a terminal 120, and by way of a diode 121 to a terminal 122.

Terminals 120 and 122 constitute command inputs to the amplitudodiseriminator and counter units 11 and 12. Application of ground potential to terminals 121) and 122 initiates the operation of the amplitudc-discriminating and counting circuitry (not shown) in units 11 and 12, to count the pulses from detector output line 24 passed by unit 11, and having peak amplitudes determined by the presetting of controls 25 and 26, and for the time period determined by the presctting of control 27. On completion of the counting period, the count arrived at is recorded by the printing unit 13 together with the identification number of the sample just tested (ie. sample No. 1) on a suitable medium such as a tape. Obviously the printing unit 13 may be replaced or supplemented with any other type of recorder, e.g. a card or tape perforating unit, or a display.

The printing unit 13, on having completed the printing operation, issues a command signal in the form of a voltage pulse applied to terminal 123, which energizes a relay winding 124 and closes associated contacts 125. This applies ground potential by way of contacts r3a', closed at this time, to input of the monostable circuit No. 1.

Each of the monostable circuits No. 1 and No. 2 has power inputs 11.3 or 114 respectively, connected in parallel to the A-C lines 105406 and has a ground connection 115 or 1.16. When both the power inputs and the ground line of either circuit are effectively connected, the circuit tlips" to its unstable state for a definite period, here about 1 second. In this state a voltage is applied to an output relay winding of the circuit. respectively R11 and R12, and associated contacts 111 or r12 are closed.

it. will be noted that monostable circuit No. 2 has its power inputs 114 connected across A-C lines lS-ltl6 by nay of normally open contacts r711, whereas circuit No. 2 has its power inputs 113 continuously ctr crgizcd from the A-C. lines. Hence, the application of ground potential to input 115' causes the output relay winding kit of the circuit to be energized for one second, with a corresponding closure of contacts rll. This in turn causes cncrgization of relay winding R4 from D-C line lll.

linergization of R4 closes normally open contacts r-tn whereby the D-(.. potential from rectiiier bridge 107 is applied to energize the latch solenoid S2, thereby releasing the turntable indexing gear 8 for rotation. Encrg' .ation of relay R9 likewise opens contacts r-lh, preventing subsequent cncrgization of stepping solenoid S3.

Latch solenoid $2. on being energized to release the index gear ti and turntable for rotation, simultaneously reverses the osition of switch SW1, thereby energizing relay winding R5.

Energization of relay R5 closes relay contacts and r512, applying alternating power from lines 105-106 across the A-C turntable motor M2. The motor starts revolving, carrying with it indexing gear 8, and turntable 3.

As the turntable 3 s arts to revolve. a stop, not shown, carried by it acts on s"- itch sn'Z energizes relay winding R7 after a short delay as determined by the time constant of resistor 126 and capacitor 127. Contacts r71) close, establishing a holding circuit for relay R7 through normally closed contacts rSc switch r70 reverses without immediate ellcct since contacts r-tb are open.

After the time constant, about one second herein, of monostable circuit No. 1 has lapsed, its output relay R11 is dcenergized opening contacts 111 and dcenergizing relay R4. Contacts r-ia return to their normally open position decnergizing latch elcctromagnet S2. Therefore, as the turntable 3 reaches its next indexing position, the. latch drops into the corresponding notch of the index gear 8, latching it i t position. (ontncts nth are returned to their normally closed position. Solenoid S3 is now energized through normally closed contacts 19a and 1'41) and switch contacts r711 now in reversed position owing to the cncrgization of relay R7. Energization of solenoid S3 steps the rotary switch arm 112 to contact Nr.- 2.

As latch solenoid S2 is dcenergized and drops into latching engagement with index gear 8 at irldCX position Nr. 2, it causes switch SW1 to return to its normal position (shown), thereby energizing relay winding R9. Contacts r9a are opened, deenergizing stepping solenoid S3. Contacts r9b are closed, thereby applying ground potential through contacts r30, now closed, to the stepping switch arm 112. Through stepping contact Nr. 2 this ground potential is applied by way of a diode 128 to one of a pair of contacts controlled by a manual test selector key K2. Key K2 and the similar keys K3-K12 associated with the respective stepping contacts Nrs. 2 to 12, and only the. first and last of which are shown, serve to preselcct the specimen it is desired to analyze. Depression of any oi these keys (which are provided with means not shown for latching them in depressed position) will ensure that the corresponding specimen 2-012 will actually be subjected to test when it reaches testing position. Where a key K2-Kl2 is not depressed, the amplnude-discrimination unit 11 will not be energized to gate pulses to digital counter 12, the printing machine 13 will be commanded to print a zero together with the number of the specimen, and the turntable will be indexed to the next position.

This provision for selecting the sam le positions that are to be effectively subjected to the testing procedure constitutes an advantageous feature of the invention. It can often happen that it is only desired to test a small number of specimens, less than the full complement (herein twelve) the turntable 3 is adapted to receive. in

such cases it would clearly be a waste of time and power as well as a source of error, if the complete testing procedure, including the count of ionization pulses for the selected period, eg. 30 seconds, were to be carried out for those indexed positions of the turntable at which no useful example is present. The means being described avoids this. it will be noted that no means are provided for omitting the test at indexed position Nr. 1, since pres-umably at least one sample is to be analyzed if the apparatus is being used at all.

Assuming then selector key K2 has been depressed, the ground potential from stepping contact Nr. 2 is applied through diode 128 and the closed contacts of key K2 to terminal 126, and through diodes 128-129 in series to terminal 122. When both these terminals are at ground potential, the units 11, 12 and 13 operate in the manner earlier described to count the discharge pulses gated by unit 11 for a selected period of time (c.g. 30 seconds), and print the count together with the specimen number (Nr. 2) on a record sheet. If however the ground potential signal from contact Nr. 2 is applied only to terminal 1.22 but not to terminal due to selector key K2 not having been depressed, then the printing unit 13 is controlled through means not shown to print immediately a zero and the sample number upon the record sheet.

In either case on completion of the printing operation a command voltage signal is applied from printer 13 to terminal 123 energizing relay 124 to apply through contacts 125 a ground potential to the input 15 of monoslablc circuit No. 1.

This initiates a fresh stage of the cycle entirely similar to the one just described except that it will involve the sample position Nr. 3 of the turntable. The turntable 3 is thus indexed through its successive positions and any useful samples present therein are analysed and the corresponding counts are printed on the record sheet together with the identification numbers of the corresponding samples (as well as any other desirable indications). The repetitive operations involved in these cycle stages will not again be described, and only the last stage occurring after the turntable 3 has rotated past sample position Nr. 12 will be discussed, since this involves the operation of the end-of-cycle monostable circuit No. 2.

The initial steps of the stage are as earlier described, monostable circuit No. 1 is energized for a period of one second, energizing relay R4 for a corresponding period. At the end of this period relay R4 is dcenergizcd and its contacts r451 return to open condition, dcencrgizing latch solenoid S2. Contacts r41) are closed providing an energizing circuit for solenoid S3 through r7u in reversed condition and in normally closed condition. Energization of solenoid S3 steps the arm 112 to position Nr. 1. As the turntable approaches its position Nr. 1 a stud provided on the index gear 8 actuates switch sw2 to return it to its normal position shown, whereby ground potential is applied to input 116 of monostable circuit No. 2. Since at this time relay R7 is energized, circuit No. 2 is energized through contacts r7c from A-C lines 105-106 so that application of ground potential to its input 116 now energizcs the monostable circuit No. 2 which delivers an output energizing relay winding R12. Contacts r12 close, providing cncrgization for relay R8.

Energization of relay R8 causes contacts rBIi to open, dcencrgizing relay R3. Encrgization of relay RS also causes opening of contacts r811, dccnergizing relay R1. Lastly cnergization of relay R8 causes opening of contacts rtic, dcenergizing relay R7.

Deenergization of relay R1 opens the contacts rib, cutting oil the energizing circuit for vacuum pump motor M1 and solenoid S1. Hence the power is cut oil from vacuum pump 10, and vent valve 14 is moved to a position in which it vents the interior of the enclosure under bell cover 4 to atmosphere. This will enable the bell cover t be easily lifted off the table 16.

Deenergization of relay R7 causes rcverser contacts the stepping snitch arm H2.

As the turntable 3 reaches indexing position Nr. 1, latch 9 is allowed by deenetgized solenoid SI. to drop into the corresponding notch in the index wheel. latching the turntable at this position. The movement of the latch simultaneously moves the reverscr switch and to its normal position, providing a circuit for the continued ener gization of relay R9, and cutting oil the. energizing circuit for rcla R5.

Deenergization of relay 5 opens its contacts r511 and 15!, cutting off the turntable motor M2 from the power lines.

The bell'eover 3 can now be lifted off (since its interior has been vented to atmosphere as indicated above), and this action acts mechanically to interpose shutter 5 in front of the X-ray tube window 20. permitting safe manipulation. The samples 0l-e12 can be removed from their mounts on turntable 3 and fresh samples inserted in their stead. Desirably, the turntable 3 is arranged for bodily removal from off the top of shaft 18, and another identical turntable. not shown, carrying a complement of fresh specimens which have been manually inserted thereon by the operator during the automatic testing cycle described, can he substituted therefor on the shaft 18. After fresh specimens have been positioned in either of the two ways just referred to. the bell cover 4 may be replaced, this moving shutter 5 clear of the X-ray tube window 20. The cycle start key Kl can then be depressed to initiate a fresh testing cycle. l\-leanwhile of course, the various controls previously discussed may have been readjusted if desired, and the test selector keys K2-K1Z reset.

Means are shown whereby the samples can be recycled for another round on the turntable 3 should it he desired to subject them to a further round of tests. When it is desired to do this a recyele" reverser switch 130 connected between relay winding R8 and ground is thrown manually to its Recycle position-In this'position ground is cut oil from winding R8 and connected instead through a connection 13L (only partly shown in the drawing) to one terminal of a neon lamp 132 the other terminal of which is connected to a DC output terminal of rectifier bridge 107. The lamp lights up to indicate the recycle condition. In this condition. it will be evident from the explanation given that: the end-of-cyele" monostable circuit No. 2 will remain inoperant to terminate the cycle. Specifically, relay RS will remain deenergized owing to its disconnection from ground, and hence relays R3, R1 R7 will remain energized. The indexing of the turntable and the testing procedure at each stage will then continue for another round, and for successive rounds so long as the recycle switch 130 is retained in recycle position.

In a preferred modification of the automatic control and programming unit partly illustrated in FIG. 4. means are provided for pre-selecting, in connection with each sample presented to testing position, not only the bare fact whether or not. the samp e is to be tested, but also the values of the parameters that are to be used in connection with each of the samples that are tested. These parameters may include as will be understood from previous explanations 'lhreshold voltage of the pulse peaks gated through amplitudodiscriminator unit ll; Gateavidth voltage of said gated pulse pealts; Counting time in digital counter 12.; High-tension voltage applied to X-ray tube 1; Current flow through X-ray tube 1.

For the purposes of this detailed selection of the. test parameters there are schematically shown in l-lG. -'l five series of potentiometers, each series including twelve po tentiomcters (not all shown). All the. potentiometers of a first series, designated THI to T1112, have one side of their resistors connected in common to a conductor 'lll which leads to a threshold voltage control circuit of the amplitudc-discrituinator unit It. All the otentiometer-s of a second se es GW1G .VI2 have one side of their resistors connected by a common conductor GW to a g:ttc-\itlth voltage control circuit of amplitude-discriminator unit 11. The potentiometer-s of a third series C'lb CTIZ have one side of their resistors connected by a conductor CT to the count time control circttit of digital counter .12. The potcntiornetcrs of a fourth series XV1-- XVlZ have one side of their resistors connected by conductor XV to the highwoltage control circuit in the X- ray tube supply unit 15; and the potentiometers of fifth series XCLXCIZ have one side of their resistors connected by conductor XC to a current control circuit of unit 15.

Correspondingly positioned potentiomcters in all five series have their movable contact arms connected in scries, by way of the interposed isolator diodes shown, to respective conductors leading to the twelve segmental contacts Nr. 1 to Nr. 1.2 respectively, of a rotary stepping switch RS. Thus, at each position of the rotary switch arm 11?. (stepped by solenoid S3) and hence at each testing position of turntable 3, the ground potential present on switch arm 112' will be applied to only a corresponding one out of the twelve potentiometers in each Of the live series. It will be evident that by separately presetting the movable potentiometer arms it is possible to preseleet the values of the test parameters used for each of the samples mounted on the turntable.

This makes it possible to test different samples mounted on the turntable 3 for different constituents. The samples may of course be specimens taken from the same or different batches of material, and the arrangement described provides the possibility, among many others, of accurately and quickly determining the proportions of a range of consti... run of the apparatus described.

A practical form of construction of the sample changer and X-ray analysis assembly schematically described above in connection with FIGS. 1 and 2, will now be described with reference to the more detailed views of FIG. 5, 6 and 7.

The domed bell-like cover 4 is seen to be pivoted at one side to the table or baseplate 16 by means of the horizontal pivot 7.0L and a handle 202 projecting from the opposite side of the bell cover 4 enables this cover to be conveniently rotated manually about its pivot for lifting it off the top of table or baseplate 16 and lowering it back into position in scaling engagement with the baseplato. The turntable 3 is seen to include a hub pt rt 203 and a flanged rim part 204 removably secured thereto by means of one or more locator studs 2G5. The hub 203 is keyed at 206 on the reduced upper part of vertical shaft 18 and secured thereon with a nut 267, and is rotatably supported upon the baseplate 16 by way of an annular thrust bearing 208. Shaft 18 includes an intermediatecliameter section which extends through a hat-shaped bearing member Zitl mounted in a bore of the baseplate l6 and secured thereto with screws 211 extending through holes formed in the horizontal flange of the member 210 into holes formed in the undersurface of bascplate 16. The said shaft section is supported for rotation in bearing member 210 by way of a conical roller thrust bearing 212 and an annular scaling gland 213 is lodged in a re eat elements in :1

i sin'"le ceSs surrounding the shaft above the roller bearing 212.

An enlargedaliamcter section 2 14- of shaft 18 abuts the lower inner race of thrust bearing 212 and cooperated with nut 207 to retain the parts in assembly.

Spacer posts 2i5 have their upper threaded ends screwed into holes formed in the flange of bearing member 210 and project dowmvard therefrom to support a horiuimtal motor-ntotmting plate 216 secured to the lower ends of the posts with screw studs. The motor M2 serving to drive the shaft 18 and turntable 3 is attached by means not shown to the under side of plate 216 and the motor output Spindle 217 projects upward through a central hole in said plate. The motor spindle 217 has a di kdikc friction coupling member Zltl non-rotatably secured around it a short distance above mounting plate 216 by means such as a grub screw eng ging the spindle.

The indexing wheel 8 is in two parts, including a hub part 2.19 and a peripheral part 220 secured thereto with screws. The peripheral part 220 has twelve notches such as 221 formed around its outer periphery for the purposes of the indexing function. The hub part 2T9 of indexing wheel 8 has a central aperture which is non-rotatably slidable around the lower end of a stud member 222 which projects from the lower end of shaft 18 and forms a unitary extension of said shaft. A compression spring surrounding a central boss of part 219 presses said part down so that its under surface frictionally cngages the friction surface of coupling disk 218. The upper end of spring 223 is abutted by the lower end of an inverted cup-shaped member 224 slidable around stud member 222 and abutted at its upper surface against a nut adjustably screwed on a threaded section of stud member 222 in order to control the pressure of frictional engagement of the friction coupling.

The casing of latch control solenoid is supported from stationary structure not shown in fixed relation with metor M2 at one side of index wheel 8. The latching armaturc 226 cooperating with the solenoid has a tapered latching nose inscrtable into any one of the notches 211 by the action of a spring on decncrgization of the solenoid.

The microswitch .swl is secured to the casing of solenoid S2 at the under side thereof and its switch actuator element projects upwards as shown into the path of an annular rib surrounding the latching nose of armature 226 so as to be actuated on decncrgization of the solenoid as earlier explained herein.

The microswitch .rwZ is supported through a bracket from the upper side of the solenoid casing and its actuator clement projects downward so as to be actuated by a stud 228 projecting upward from the periphery of the indexing gear 8. It will be recalled that switch SW2 is to be actuated by stud 22S once per revolution of the indexing wheel and turntable 3 so as to be returned to its normal position in order to initiate cnd-ot-cycle functions. Accordingly stud 228 is positioned at a suitable setting on indexing member 220 between the notches 221 which correspond to sample position No. 12 and sample position No. 1.

Returning to the turntable 3, the rim member 294 thereof has twelve pairs of radially spaced holes 229 formed around its flanged periphery for the afiixing of twelve sample mounts such as 230 thereto by means of studs inserted into said holes. Only one sample mount is shown. The sample mounts are small rectangular frame members conveniently made of an epoxy resin (such as Aralditc), having means for rcmovably securing therein the rectangular samples such as c1. which herein are 3 millimeter thick test pieces of. rubber to be analyzed for sulfur content. The samples are adapted to be supported in the mounts 230 with an outer face thereof accurately located against a locating surface surrounding the inner periphery of a rectangular window formed in the sample mount. A retainer block 232 of suitable material and centrally perforated for the escape of entrapped air, it can be blocked in position behind the specimen 01 by means of a set screw 233 threaded into the top of. the mount.

As earlier indicated a convenient practical procedure is to remove the turntable 3 with all the samples thereon bodily from the apparatus and substitute another turntable wtih fresh samples prepared at a separate station. This is greatly facilitated by the construction shown wherein the rim part 20-1 of the turntable can be lifted off the i ihub part 203 by means of the grips 244 projecting thercfront, and can be reinserted in a prescribed setting r t tive to the hub owing to the provision of the locator pin or such as 205.

The movable safety shutter 5 which serves to mask the X-ray beam when the bell cover 4 is lifted from its operative position as earlier described, is best seen in FIG. 7. The shutter 5 is in the form of a rigid strip of suitable material opaque to X-rays and is pivoted at an intermediate point about a horizontal pivot 245 on a suitable support upstanding from bascplatc 16. The support may constitute the casing of counter tube 2. A tension spring 246 has its ends attached to the inner extremity of shutter 5 and to a suitable anchor point on the baseplate so as to urge the shutter to its masking position, shown in dot-dash lines, in which it masks the window 20 of the X-ray tube 1 through \vhichthc X-ray beam issues. The outer end of shutter 5 beyond pivot 245 carries a laterally projecting bracket 248 the upper surface of which is engageablc by an actuator lug 2% project ing downward from an arm 250 supported from a sidewall of cover 4. As shown, in the normally lowered position of cover member 4, the lug 249 acts to depress the bracket 248 and thereby move the shutter S to its upper position shown in full lines against the tension of spring 246. In this position shutter 5 is clear of the X-ray beam. When however the domed cover 4 is lifted the lug 249 discngagcs the flange 2-58 and the shutter returns under the bias of spring 246 to the lowered position shown in dot-dash lines, in which it masks the beam issuing from window 20 and thus permits manipulation without danger of irradiation to the operator.

Both tle X-ray generator tube 1 and the ionization counter 2 are generally standard pieces of equipment manufactured and sold by the assigncc, Compagnie Genralc do Radiologic. More specifically the X-ray tube 1 used was similar to the tube embodied in the assigncc conipanys X-ray analysis unit sold by the trade name Cristallobloc in which the cathode was angularly displaced 6 for convenience. The ionization counter 2 was a modified form of the continuous gas-tlow proportional counter marketed as DM. 160.

It will be noted especially from FIG. 6 that the geometry of the X-ray tube 1 and ionization counter 2 as mounted with respect to the test sample (21 in testing posi tion is so arranged as to provide an extremely compact disposition with the sample positioned very close to the windows of the tube and counter, and in such an angular relationship thereto as to be seen under relatively large, equal mean solid angles both from the X-ray tube 1 and the ionization counter 2.

Example The non-dispersive X-ray analysis apparatus substantially in the form disclosed with reference to FIGS. 5-7 was developed for use as a productiondnspcction appliance in the' workshops of a tire manufacturing plant, the Compagnie, des Pncumatiques Michelin, Clcrmont-Ferrand, France, for the determination of sulfur content in the rubber stock. The sulfur content could vary over a range of from 1% to 6% and the relative accuracy of the determination specified was to within of the sulfur content. The rubber stock contained substantial amounts of zinc oxide. The rubber specimens used were rectangular strips 20 by 30 millimeters ranging in thickness from 1 to 3 mm.

The amplitudc-discriminator It and digital counter 12 3G. 2) were embodied in a unit marketed as the ANC 660 Spccitroscaler by Atcliers dc Constructions Electriques do Charleroi, S.A., Charleroi (Belgium), an affiliate of the assignce company. The printing unit 13 used was the abovoidcntified manufacturers MAJ. 100."

The enclosure was evacuated to a pressure of 10* torr.

The X-ray high-voltage supply unit 15 was regulated 15 in an output voltage constant to within 1!)" and was set to h siiovults and 1 ma. reasons earlier indicated.

The counter was supplied under a voltage of 1350 volts, and the pulses were pa ed thtough an amplifying chain or -1 dl. attenuatitm and prmiding a gain of 50 in the preamplifier stage and ltttlt tl in the at'npliiier stage.

An initial calibrati n of the apparatus was carried out by mic a ample of gra; containing 5% sulfurx and the curse drown in t lt ,1. b earlier referred to was plotted. l! ad-t thus found that the sulfur peak could he satisiznttuily gfalt'tl b1. adju. the control 25. 26 of the u nphtudc dixriminz'ttor 't it to a \oltage gating threshuid of to volts and a gate width of lb \oits, as shown in the graph To calibrate the system oter the entire range of sulfur concentrations specified, seven specimens of known sulfur utttlcfii etc passed through the appu ms and the average number of diwharge pulses per second over thirtyeeond periods as indicated by the digital counter unit 12 for each pecimen were recorded. the results are pitch in the fotlouing table.

: ainple No. S l ise'. urges per second 'l'hese results are plotted in the graph of FIG. 9 with sulfur content percent in abscissa and pulses per 30 seconds in ordinates.

The curve shows a good degree of regularity and a slope (sensitivity) steep enough to provide the specified degree of relative accuracy with counting times not excccding 30 seconds. Higher accuracies can of course be achieved simply by increasing the counting time beyond thirty seconds. The results were found to be relatively unaffected by the surtacc condition oi the samples. On the other hand, the precise positioning of the tested sample surface with respect to the X-ray tube and the ionization counter against the locating surface of sample mounts 230 has been found to be of considerable importance especially in the case of thin samples.

Of the many possible variations and modifications conceivable by those familiar with the art without departing from the scope of the present invention, one modification will be specif cally referred to herein because of its potential importance. This concerns the possibility of testing a sample while positioned at the analyzing station for two (or more) different constituent elements simultaneously. It will be evident that the programmer circuitry of FIG. 3 and/or P16. 4 can be modified in simple ways (for example by providing therein an additional rotary switch similar to the one shown in FIG. 2 or 3, and having its switch arm rotated stcp-by-step by means of solenoid S3), so that the amplitude-discominator unit 11 will simultaneously gate through different gating channels thereof two (or more) pulse trains from ionization detector output lead 24 having different, preselected, peak amplitude values. These pulse trains of different amplitude can be directed to separate digital counters such as 13 (or to different counting channels of a common digital counter) in order to indicate simultaneously the amounts of diffcrent, selected, constituent elements present in the sample.

What I claim is:

1. Apparatus for X-ray analysis comprisin":

an X-ray generator;

21 sample carrierindcxablc to present each of a series of samples to an analyzing station adjacent the generator to be irradiated with an X-ray beam;

means for indexing the sample carrier;

an ionization detectonpositioned adjacent the analyzlug station to be irradiated with a secondary beam re- 1 6 emitted by thesamplc and producing ionization di charge voltage pulses corresponding in eak ttmplj. tudc to various constituent elements of. the sample andat rates corresponding to the proportions of said elements in the sample;

electronic gating and counting means connected to r ceivc said pulses from the detector and to count those pulses having peak amplitudes in a selected range;

means operative on termination of a count by said electronic means to advance the sample carrier to present a next sample of the series to the analyzing station;

and prescttable adjusting means associated with said indexing means and said X-ray generator for adjusting the voltage and current of the generated X-ray beam to desired values in each of the indexed positions of the sample carrier.

2. Apparatus for X-ray analysis comprising:

an X-ray generator;

a sample carrier indexable to present each of a series of samples to an analyzing station adjacent the generator to be ir adiate with an X-ray beam;

means for indexingthe sample carrier;

an ionization detector positioned adjacent the analyzing station to be irradiated with a secondary beam re emitted by the sample and producing ionization discharge voltage pulses corrcsponding in peak amplitude to various constituent elements of the sample and at rates corresponding to the proportions of said elements in the sample;

amplitude discriminating means connected to receive said pulses from said detector and to gate only those pulses having peak amplitudes in a selected range to an output of said amplitude discriminating means;

digital counter means connected to said output to count the pulses gated thereby;

means operative on the termination of a count by said digital counter to advance the sample carrier to present a next sample of the series to the analyzing staand prescttable adjusting means associated with said indexing means and said digital counter means for adjusting the counting time over which the gated pulses are counted in each of the indexed positions of the sample carrier.

3. The apparatus claimed in claim 2, including record ing means connected to the digital counter for recording the count obtained thereby, and including means responsivc to the termination of a recording operation to advance the sample carrier to present a next sample of the series to the analyzing station.

4. The apparatus claimed in claim 2, including means prescttable for preventing the digital counter from Ttl'dliing a count for any non-elected samples of. the series.

5. Apparatus for X-ray analysis comprising:

an X-ray generator;

a sample carrier indexable to present each of a series of samples to an analyzing station near the generator to be irradiated with an X-ray beam;

means for indexing the sample carrier;

an ionization detector positioned near the analyzing station to be irradiated with a secondary beam rccmitted by the sample and producing ionization discharge voltage pulses corresponding in peak amplitude to various constituent elements of the sample and at rates corresponding to the amounts of said elements in the sample,

amplitude discriminator means connected to receive said pulses and adjustable to gate only those pulses having peak. amplitudes in a selected range corresponding to a selected element, to an output of the amplitude discriminator means;

digital counter means connected to said output to count the gate pulses;

means operative on termination of a count by said digital counter to advance the sample carrier to pm" 3,39l,2(d 17 I 18 sent a next sample of the series to the analyzing stned on movement of the cover member to scaling position lion; mid to move the shutter to clear position. prcsettahle adjusting means connected to the indexing 9. The apparatus claimed in claim 6, including presetmeans and the amplitude discriminator tor prc.-.ettiug table means in the Controller unit connected with said the amplitude range of the. pulses gated. thereby to a analyzer means for selecting the amplitutlornnge of the selected range in each of the indexed positions of the pulses counted thereby during Picscmilllon of each sample carrier. sample. 6. Ap aratus for Xaay analysis comprising: 10. Apparatus for X-ray analysis comprising: a scalable enclosure; an enclosure conncctable to a vacuum source; an .\'-ray generator in the enclosure; an X-ray generator in the enclosure having a removable a sample carrier in the enclosure intermittently discover;

placcahle to present each ot a series of samples to an a turntable in the enclosure carrying a series of samples analyzing station to he irradiated with an X-ray beam spaced around its periphery and intermittently rofrom the generator;' tatable to present each sample in succession to an an ionization detector positioned in the enclosure to be analyzing station near the generator to be irradiated irradiated with a secondary hcam rccniitted by the with an X-ray beam; sample and producing voltage pulses corresponding a detector positioned in the enclosure to be irradiated in peak amplitude to various constituent elements of with a secondary beam emitted by the sample and the sample and at raics corresponding to the proporproducing voltage pulses corresponding in peak amtions of said elements in the sample; plitude to various constituent elements in the sample; electronic analyzer means connected to the detector for electronic L'- alyzcr means connected to the detector for counting the pulses in a selected range or peak amcounting the pulses in a selected range of peak amplitudes; plitudes; a source of vacuum conncctable with the encl sure and means operative on termination of a count to advance means for venting the enclosure: and the turntable to'present a next ample to the analyzan electric controller unit cnergizable to initiate a tcsting station; l

ing cycle, said unit including: means for connecting said enclosure with said vacuum means Operative at the start oia cycle to connect source at the start of a testing cycle and means for the enclosure with the vacuum source, means venting the enclosure at the termination of a testing connected with the sample carrier for intcrmit- 3o cycle, whereby the cover can be removed; and tcntly displacing the sample. carrier to present removable shutter means in the enclosure and means each sample of the series in succes ion to the actuated on removal of the cover to move said shutanaly'zing station, means connected with the tcr means to a position in which it masks the X-ray electronic analyzer means to ener ize same for beam from said generator to permit safe manipulacounting said pulses during presentation of each 35 tion in the enclosure after removal of the cover. sample, and means operative attcr resentation 11. The apparatus defined in claim 10, including means of the last sample of the series to disconnect for bodily removing at least part of said turntable to the enclosure from the vacuum source and vent gcther with the tested samples carried thereby from out the enclosure. of the enclosure after removal of the c and for bodily '7. The apparatus claimed in claim 6, wherein said conto inserting another turntable carrying further samples to troller unit includes a recycle control operable to prebe tested. vent disconnection and venting of the enclosure after References Cited presentation of said last sample and to initiate a further UNITED STATES PATENTS testing cycle.

8. The apparatus claimed in claim 6, including a cover its 3*102952 8/3263 Hfmdes ct 25O-5L5 member for said enclosure movable between an open and 2,146,347 Zleglcr et a sealing position, a movable shutter in the enclosure 4/1965 Hague Ct 31 '3 3,263,078 7/1966 'lhacltara et al. 250-51.)

movable between a position in which it masks the X-ray beam from the aenerator and a clear position and means a t i 4 4 actuated on movement of the cover member to open po- 50 kALI H Sition to move the shutter to masking position and actuat- A. L. BIRCH, Assistant Examiner. 

